Process for the preparation of vanillin and vanillin derivatives



Patented Apr. 3, 1951 PROCESS Fon THE PREPARATION OF VANILLIN AND VANILLIN DERIVATIVES Paul Lagally, Aschaffenburg Main, Germany, as-

signor to Aktiengesellschaft, Germany Aschaffenburger Zellstoffwerke,

Redenfelden/Oberbayern,

No Drawing. Application February 13, 1950, Se-

rial No. 144,038. I In France June 16; 1948 1 The present invention relates to a-process for the preparation of vanillin and vanillin derivatives from lignin or lignin-containing material. It is known to prepare vanillin by sublimation and alkaline boiling of lignin-containing materials. As shown more particularly by the work of Freudenberg (see, for example, Swedish Patent No. 102.171), the yields of vanillin according to this known procedure may be increased by the supplemental use of air or oxygen. A favorable yield has'also followed from the supplemental use and careful pro-port oning of other oxidizing agents. Although unfavorable results have been obtained with potassium permanganate, hydrogen peroxide, Beckmanns mixture (bichromate-i-sulfuric acid+water), Freudenberg has successfully employed nickel oxide, cobalt oxide, manganese dioxide, and more especially aromatic nitro compounds. pounds, being water-insoluble substances, are effective only in heterogeneous phase, they require the employment of an autoclave provided with a stirrer. Moreover, in the-case of the organic nitro compounds, the starting substances can not be recovered, but are converted into aniline and similar products.

Since all these com- 5 Claims. (Cl. 260-600) alkali. The process of the present invention is therefore carried out at a temperature above 100 (dioxideof Michlers ketone); pyridine-N-oxide;

A primary object of the present invention is pounds are the sulfoxides and sulfones which are the development of a process whereby the aforesaid prior art defects are obviated.

This object is realized according to the present invention, and the aforesaid difiiculties are obviated and excellent yields of vanillin and of vanillin derivatives obtained, by carrying out the alkaline boiling in the ,presence of suitable oxygen-transmitting, water-soluble organic compounds. Such compounds'comprise the oxides of higher valent nitrogen, sulfur and iodine, wherein the oxygen is bound in semipolar manner, that is, wherein only the one electron pair of these elements is involved in the electron sextet of the oxygen. Typical representatives of this N-methyl-piperidine-Noxide.- The readily accessible oxides of suitable alkaloids with tertiary nitrogen, for example of strychnine or thebaine, can also be used.

When use is made of compounds of higher valent sulfur, the reaction temperature and reaction period must generally be increased. Under these circumstances, these compounds constitute effective oxygen transmitters in the preparation of vanillin and its derivatives according to the invention. Preferred compounds within this category are the insoluble sulfideswhich form sulfoxides and'sulfones which are either water-soluble or at least of limited solubility in hot water. Typical representatives of these comobtainable from dimethyl sulfide, diethyl sulfide, di-isopropyl sulfide, tetramethylene sulfide, methyl-cyclohexyl sulfide, etc. i

As compounds of higher valent iodine, use may be made of aromatic iodine compounds, and also ample,

class'of jcompounds areillustrated by the following formulae:

of aliphatic iodine compounds wherein the iodine atom is in an ethylene linkage. Typical representatives of these iodine compounds are, for exiodosobenzene, iodobenzene, p-propyliodobenzene, p-propyl-iodosobenzene, o-iodosotoluene, o-iodotoluene, iodoso-m-xylene, iodo-mxylene, 4 iodoso-acetophenonad iodo-aceto phenone, iodoso-anisole, iodoanisole,' iodosochlorethylene, iodo-chlorethylene, iodo-fumaric acid-iodoso-chloride, iodoso-iodoacrylic acid.

Most of these aforesaid oxygenating compounds according to the invention have an adequate solubility in water, while someof them, such as many amine oxides, are markedly hygroscopic.

After completion of the reaction, the starting materials can be readily recovered by conventional procedures such as distillation, crystallization, etc., and can be reutilized after conversion back into the state of higher valency.

The preparation of the amine oxides, which are preferred reactants, can be carried out with suitable oxidizing-agents such as hydrogen peroxide, Caros acid or by anodicoxidation.

In analogous manner, sulfoxides and sulfones may be obtained smoothly and usually quantitatively from the sulfides by the action of hydrogen peroxide. Furthermore, many of the representatives of this class, i. e. the sulfur-containing compounds, are accessible in simple manner by Example 1 In 1000 parts by volume of waste sulfite liquor having a dry content of 11.5%by Weight and a. density of 1.05, 110 parts by weight of caustic soda-are dissolved, and 137 parts by weight of N,N- dimethylaniline-N-oxide are introduced into the so-obtained strongly alkaline liquor. The obtained mixture is heated for .3 hours to 160 C. in an autoclave. The reaction mixture, which contains the formed vanillin in the form of sodium vanillate, is worked up as follows:

The re-formed dimethylaniline (115 parts by weight, equivalent to 95% of the amount used as oxide) is separated or distilled off with steam. The solution is then neutralized with 100 parts by volume of commercial hydrochloric acid, excess acid neutralized with parts by weight of sodium bicarbonate, and then extracted for 8 hours with benzene under a slight vacuum. After distillation of the benzene, 6 parts by weight (equivalent to of the starting organic substance) of fairly pure vanillin crystallize out in the course of several hours. By acidifying the mother liquor, products are obtained which can be further Worked up into synthetic resin and tanning extract.

In lieu of the N ,N-dimethylaniline-N-oxide in this example, use mayalso be made in analogous manner of an equivalent amount of tripropylamine-N-oxide, N,N,N,Ntetramethyl-diaminobenzophenone-N,N'-dioxide, pyridine-N-oxide, N-methyl-piperidine-N-oxide, etc.

Example 2 i .A mixture of 150 parts by volume of fermented and concentrated waste sulfite liquor (35 B.) obtained from pin wood, 200 parts by volume of technical caustic soda solution of 55% by volume strength (110 parts by weight of NaOI-I) and the products of the reaction between 135 parts by volume of N,N-dimethylcyclohexylamine and 85 parts'by volume of 40% by volume hydrogen peroxide, is heated to 165 C. for 3 hours in an autoclave by the forcing in of direct steam (10 .atm.). The working up of the reaction mixture (about 1000 parts by volume) is carried out according to- Example 1 and yields 130 parts by'volume of dimethylcyclohexylamine (96%) and, after neutralization and extraction, about 5 parts by weight of pure vanillin in addition to a series of benzenesoluble lignin decomposition products and resins.

Example 3 A mixture of 175 parts by volume of fermented and concentrated beechwood waste sulfite liquor with a dry content of 52% by weight, 400 parts by volume of caustic soda solution of 30% by volume strength, and the product of the reaction 4 between 63.5 parts by volume of dimethylaniline with 100 parts by volume of 35% by volume hydrogen peroxide, is heated to 165 C. for 3 hours in an autoclave. The working up of the reaction mixtur takes place as in the preceding examples.

After the recovery of 60 parts by volume of dimethylaniline, 4.5 parts by weight of a product which consists essentially of syringa-aldehyde can be obtained from the neutralized aqueous solution with the aid of benzene. A slight yield of Icy-products in the form of the usual lignin decomposition products (phenols and aromatic aldehydes) is also obtained.

Example 4 A mixture of 150 parts by volume of fermented and concentrated waste sulfite liquor obtained from pine wood, 400 parts by volume of caustic soda solution of 30% by volume strength, andthe product of the reaction between 108 parts by vol-. ume of diethyl sulfide and parts by volume of 35% by volume hydrogen peroxide, is heated to 200 C. for 10 hours in an autoclave. Upon com-.v pletion of the reaction, '76 parts by volume of diethyl sulfide are distilled off with steam and, after. neutralization and extraction with benzene, about 4 parts by Weight of fairly pure vanillin are obtained. Instead of diethyl sulfoxide, use may also be made in analogous manner of an equivalent amount of diethyl sulfone, produced from diethyl sulfide with a double quantity of hydrogen peroxide, as well as also of equivalent amounts of the sulfoxides and sulfones obtainable from di-. methyl sulfide, di-isopropyl sulfide and tetramethylen sulfide.

Example 5 A mixture of parts by volume of fermented. and concentrated waste sulfite liquor (35 Be.)- obtained from pine wood, 500 parts by volume of caustic soda solution of 22% strength by volume, and a suspension of 56 parts by weight of iodosobenzene in 150 parts by volume of Water, is heated to C. for 3 hours in an autoclave. The Work--v ing up of the reaction mixture is effected as in the preceding examples. First, 35 parts by weight of iodobenzene are distilled off with steam; the remaining aqueous solution is neutralized with parts by volume of concentrated hydrochloric acid, and 3.2 parts by weight of crude vanillin are then extracted with benzene. After recrystallization, 2.5 parts by weight of pure vanillin are obtained.

The iodosobenzene used in this example may be replaced by corresponding quantities of any of the compounds of higher valent iodine hereinbefore enumerated.

Having thus described the invention what is claimed is:

1. A'process for the preparation of vanillin and vanillin derivatives from lignin, which comprises heating the lignin to a temperature above'100" C. with a water-soluble organic oxygen liberating compound, liberating oxygen at a temperature of above 100 C. and selected from the group consisting of and the spent water soluble oxygen liberating compound is removed from the reaction mixture, reoxidized and recycled for use with additional lignin being treated.

PAUL LAGALLY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Schulz Jan. 16, 1940 Number 

1. A PROCESS FOR THE PREPARATION OF VANILLIN AND VANILLIN DERIVATIVES FROM LIGNIN, WHICH COMPRISES HEATING THE LIGNIN TO A TEMPERATURE ABOVE 100* C. WITH A WATER-SOLUBLE ORGANIC OXYGEN LIBERATING COMPOUND, LIBERATING OXYGEN AT A TEMPERATURE OF ABOVE 100* C. AND SELECTED FROM THE GROUP CONSISTING OF 